WO2017145559A1

WO2017145559A1 - Fuel injection device

Info

Publication number: WO2017145559A1
Application number: PCT/JP2017/000943
Authority: WO
Inventors: 宗尚堀部; 友基藤野; 淳川村; 鈴木　雅幸; 里志菅原; 石塚　康治
Original assignee: 株式会社デンソー
Priority date: 2016-02-24
Filing date: 2017-01-13
Publication date: 2017-08-31
Also published as: JP2017150391A; DE112017000976T5; JP6458747B2

Abstract

A fuel injection device that injects fuel from injection holes (44), and that is equipped with: a valve body (40, 240) in which the injection holes and a supply flow path (41) supplying fuel to these injection holes are formed; a valve member (60) that opens/closes the injection holes when displaced relative to the valve body; a drive unit (30) that generates driving force that displaces the valve member; a first piston member (80, 280) that partitions at least a portion of an oil-tight chamber (71, 271) filled with fuel and compresses the fuel in the oil-tight chamber by means of the driving force of the drive unit; and a second piston member (90, 290) that partitions at least a portion of the oil-tight chamber (71, 271) and is pressed by the fuel in the oil-tight chamber, thereby changing the direction of the driving force applied to the fuel in the oil-tight chamber and transmitting the driving force to the valve member.

Description

Fuel injection device

Cross-reference of related applications

This application is based on Japanese Patent Application No. 2016-33519 filed on February 24, 2016, the contents of which are incorporated herein by reference.

This disclosure relates to a fuel injection device that injects fuel from an injection hole toward a combustion chamber.

Conventionally, as disclosed in, for example, Patent Document 1, the valve member is directly displaced by the driving force generated by the drive unit without using a part of the fuel for the displacement of the valve member for opening and closing the nozzle hole. A so-called direct-acting fuel injection device is known. In addition, in the fuel injection device of Patent Document 1, a lever device is provided between the drive unit and the valve member. The lever device changes the direction of displacement by the drive unit by a mechanical lever arm, specifically, reverses 180 ° and transmits the result to the valve member.

US Patent Application Publication No. 2009/0200406

However, in the fuel injection device disclosed in Patent Document 1, the fulcrum of the lever arm slides with respect to the support portion in a state where a strong force is concentrated as the driving force is applied by the driving portion. Therefore, when the reduction and transmission of the displacement amount by the lever device are continued, mechanical wear inevitably occurs at the fulcrum of the lever arm and its support portion. As a result, there is a possibility that the change over time in the injection characteristics of the fuel injection device becomes remarkable.

An object of the present disclosure is to provide a fuel injection device that can reduce mechanical wear even when the valve member is directly displaced by a drive unit.

A fuel injection device according to an aspect of the present disclosure is a fuel injection device that injects fuel from an injection hole, and a valve body in which a supply passage for supplying fuel to the injection hole and the fuel hole is formed, and the valve body By relative displacement, a valve member that opens and closes the nozzle hole, a drive unit that generates a driving force that displaces the valve member, and at least a part of an oil-tight chamber filled with fuel are partitioned, and the oil-tight chamber is driven by the driving force of the driving unit. A first piston member that compresses the fuel and a valve member that partitions at least a portion of the oil-tight chamber and is pushed by the fuel in the oil-tight chamber to change the direction of the driving force input to the fuel in the oil-tight chamber A second piston member that transmits to

In this aspect, the driving force generated by the driving unit displaces the first piston member in the direction in which the fuel in the oil-tight chamber is compressed. Then, when the second piston is pushed by the fuel in the oil-tight chamber, the generated driving force of the driving unit is transmitted to the valve member after changing the acting direction. As described above, even if the fuel injection device displaces the valve member directly by the driving unit by changing the direction of the driving force by the fuel, mechanical wear due to transmission of the driving force is It can be reduced.

The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description with reference to the accompanying drawings. The drawing
FIG. 1 is a diagram showing an overall configuration of a fuel supply system to which a fuel injection device according to a first embodiment is applied, FIG. 2 is a longitudinal sectional view showing the fuel injection device according to the first embodiment, FIG. 3 is a longitudinal sectional view showing the operation of the displacement transmission mechanism, FIG. 4 is a time chart showing the correlation between the drive current input to the piezo stack and the displacement and injection rate of each component. FIG. 5 is a longitudinal sectional view showing a fuel injection device according to the second embodiment, 6 is a cross-sectional view taken along the line VI-VI in FIG. 8 showing the configuration of the displacement transmission mechanism. FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG. 8 showing the configuration of the displacement transmission mechanism. FIG. 8 is a longitudinal sectional view showing the operation of the displacement transmission mechanism.

Hereinafter, a plurality of embodiments of the present disclosure will be described with reference to the drawings. In addition, the overlapping description may be abbreviate | omitted by attaching | subjecting the same code | symbol to the corresponding component in each embodiment. When only a part of the configuration is described in each embodiment, the configuration of the other embodiment described above can be applied to the other part of the configuration. Moreover, not only the combination of the configurations explicitly described in the description of each embodiment, but also the configuration of a plurality of embodiments can be partially combined even if they are not explicitly described, as long as there is no problem in the combination. And the combination where the structure described in several embodiment and the modification is not specified shall also be disclosed by the following description.

(First embodiment)
The fuel supply system 10 shown in FIG. 1 uses the fuel injection device 100 according to the first embodiment. The fuel supply system 10 supplies fuel to each combustion chamber 22 of a diesel engine 20 that is an internal combustion engine by a fuel injection device 100. The fuel supply system 10 includes a feed pump (F / P) 12, a supply pump 13, a common rail 14, an engine control device 17, a plurality of fuel injection devices 100, and the like.

The feed pump 12 is, for example, a trochoid pump built in the supply pump 13. The feed pump 12 pumps light oil as fuel stored in the fuel tank to the supply pump 13. The feed pump 12 may be separate from the supply pump 13.

The supply pump 13 is, for example, a plunger type pump that is driven by an output shaft of a diesel engine. The supply pump 13 is connected to the common rail 14 by a first fuel pipe 13a. The supply pump 13 further boosts the fuel supplied from the feed pump 12 and supplies the fuel to the common rail 14.

The common rail 14 is connected to each fuel injection device 100 via the second fuel pipe 14a. The common rail 14 temporarily stores high-pressure fuel supplied from the supply pump 13 and distributes the fuel to each fuel injection device 100 while maintaining the pressure. The common rail 14 is provided with a pressure reducing valve 14b. The pressure reducing valve 14b discharges the surplus fuel in the common rail 14 to the surplus fuel pipe connected to the fuel tank.

The engine control device 17 includes a processor, a RAM, an arithmetic circuit mainly composed of a microcomputer or a microcontroller including a rewritable nonvolatile storage medium, and a drive circuit for driving each fuel injection device 100. The engine control device 17 is electrically connected to each fuel injection device 100 (see the broken line in FIG. 1). The engine control device 17 controls the operation of each fuel injection device 100 according to the operating state of the diesel engine 20.

The fuel injection device 100 is attached to the head member 21 in a state of being inserted into the insertion hole of the head member 21 that forms the combustion chamber 22. The fuel injection device 100 directly injects fuel supplied through the second fuel pipe 14 a from the plurality of injection holes 44 toward the combustion chamber 22. The fuel injection device 100 includes a valve mechanism that controls fuel injection from the injection hole 44.

As shown in FIG. 2, the fuel injection device 100 includes a valve body 40, a nozzle needle 60, a drive unit 30, and a displacement transmission mechanism 70 having a large-diameter piston 80 and a small-diameter piston 90.

The valve body 40 is configured by combining a plurality of members formed of a metal material. The valve body 40 is formed with an injection hole 44, a seat portion 45, a high-pressure channel 41, a return channel 43, and a drive unit accommodation chamber 47.

The injection hole 44 is formed at the distal end in the insertion direction of the valve body 40 inserted into the combustion chamber 22 (see FIG. 1). The tip is formed in a conical or hemispherical shape. A plurality of nozzle holes 44 are provided radially from the inside to the outside of the valve body 40. High-pressure fuel is injected from each injection hole 44 toward the combustion chamber 22. The high-pressure fuel is atomized by passing through the nozzle hole 44, and is easily mixed with air. The seat portion 45 is formed in a conical shape inside the tip end portion of the valve body 40. The seat portion 45 faces the high-pressure channel 41 on the upstream side of the nozzle hole 44.

The high-pressure channel 41 supplies high-pressure fuel supplied from the common rail 14 to the injection hole 44 through the second fuel pipe 14a (see FIG. 1). A piston accommodating chamber 42 is formed in the high-pressure channel 41. The piston housing chamber 42 is a two-stage cylindrical space provided as a part of the high-pressure channel 41 and provided in the middle of the high-pressure channel 41. The piston accommodating chamber 42 accommodates at least a part of the displacement transmission mechanism 70. A large-diameter sliding wall portion 46a and a small-diameter sliding wall portion 46b are formed on the large-diameter and small-diameter inner peripheral walls that define the piston housing chamber 42, respectively.

The return channel 43 extends along the high-pressure channel 41 in the valve body 40. The return flow path 43 is not injected from the injection hole 44, and leaks, for example, leaked fuel used for cooling the drive unit 30 to the surplus fuel pipe outside the fuel injection device 100. The pressure of the fuel flowing through the return flow path 43 is lower than the pressure of the fuel in the high pressure flow path 41. In FIG. 1 and the like, the high pressure region is indicated by a dark dot, and the low pressure region is indicated by a thin dot.

The drive unit accommodation chamber 47 is a cylindrical space that houses the drive unit 30. An insertion hole 48 is formed between the drive unit accommodation chamber 47 and the piston accommodation chamber 42. One end of the return flow path 43 is opened in the insertion hole 48. Through the insertion hole 48, a part of the fuel flowing through the high-pressure channel 41 is supplied to the drive unit accommodation chamber 47. The drive unit accommodation chamber 47 is filled with fuel.

The nozzle needle 60 is formed in a cylindrical shape as a whole by a metal material. The nozzle needle 60 is accommodated in the valve body 40 by being disposed in the high-pressure channel 41. The nozzle needle 60 can be reciprocally displaced in the axial direction with respect to the valve body 40. The nozzle needle 60 is formed with a flange portion 61 and a face portion 62.

The collar portion 61 is formed in a disk shape having a larger diameter than the main body portion of the nozzle needle 60. The flange portion 61 is provided at an upper end portion located in the piston accommodating chamber 42 among both axial end portions of the nozzle needle 60. A chamfered portion 64 is formed on the flange portion 61. The chamfered portions 64 are formed in a rectangular flat shape on both sides of the flange portion 61 in the radial direction. The chamfered portion 64 forms a flow path for circulating high-pressure fuel between the small diameter piston 90 and the flange portion 61. Between the flange 61 and the large-diameter piston 80, a coiled needle spring 63 in which a metal wire is wound spirally is arranged in a compressed state. The nozzle needle 60 is urged toward the nozzle hole side by a needle spring 63.

The face portion 62 is formed in a conical shape on the lower end surface facing the nozzle hole 44 among the axial end surfaces of the nozzle needle 60. The nozzle needle 60 causes the face portion 62 to be separated from and seated on the seat portion 45 by relative displacement with respect to the valve body 40. The face portion 62 forms a main valve portion 50 that opens and closes the nozzle hole 44 together with the seat portion 45.

The driving unit 30 includes a piezoelectric element laminate 31, a stress relaxation mechanism 32, and the like. The piezoelectric element laminate 31 is a laminate in which, for example, layers called PZT (PbZrTiO 3) and thin electrode layers are alternately stacked. The piezoelectric element laminate 31 receives an input drive signal output from the engine control device 17. The piezoelectric element stacked body 31 expands and contracts along the axial direction of the drive unit accommodation chamber 47 due to a reverse piezoelectric effect that is a characteristic of the piezoelectric element, based on a voltage or current corresponding to the drive signal. The piezoelectric element laminate 31 generates a driving force for driving the nozzle needle 60.

The stress relaxation mechanism 32 is a mechanism that transmits the expansion and contraction of the piezoelectric element laminate 31 to the displacement transmission mechanism 70 and relaxes the stress input to the piezoelectric element laminate 31. The stress relaxation mechanism 32 includes a pressure piston 33, an output piston 34, a relaxation cylinder 35, a slit spring 36, and a relaxation spring 37. The pressure piston 33 and the output piston 34 are formed in a columnar shape having substantially the same outer diameter. The pressurizing piston 33 and the output piston 34 are arranged side by side in the axial direction.

The pressurizing piston 33 is in contact with the piezoelectric element laminate 31. The movement of the piezoelectric element laminate 31 that expands and contracts is input to the pressure piston 33. The output piston 34 faces the pressurizing piston 33 with the relaxation oil-tight chamber 35a interposed therebetween. The output piston 34 is formed with a stroke portion 34 a that protrudes in a cylindrical shape toward the piston accommodation chamber 42. The stroke portion 34 a is inserted through the insertion hole 48. The front end surface of the stroke portion 34 a is in contact with the large diameter piston 80.

The relaxation cylinder 35 is formed in a cylindrical shape and is externally fitted to the pressure piston 33 and the output piston 34. The relaxation cylinder 35 defines a relaxation oil tight chamber 35 a between the pressurizing piston 33 and the output piston 34. The displacement of the pressurizing piston 33 is expanded in the axial direction and transmitted to the output piston 34 by the fuel filled in the relaxation oil tight chamber 35a.

Each of the slit spring 36 and the relaxation spring 37 is a metal spring that generates an elastic force in the axial direction. The slit spring 36 urges the pressure piston 33 toward the piezoelectric element stack 31 with respect to the relaxation cylinder 35. The relaxation spring 37 biases the output piston 34 toward the large-diameter piston 80 with respect to the relaxation cylinder 35.

The drive unit 30 transmits the expansion and contraction of the piezoelectric element laminate 31 to the output piston 34 via the fuel in the pressurizing piston 33 and the relaxation oil-tight chamber 35a, thereby reciprocating the stroke part 34a in the axial direction. As the drive current input to the drive unit 30 increases, the drive force input from the stroke portion 34a to the large-diameter piston 80, and thus the displacement amount of the stroke portion 34a and the large-diameter piston 80, increases.

The displacement transmission mechanism 70 is a mechanism that transmits the driving force of the driving unit 30 to the nozzle needle 60 by the large diameter piston 80 and the small diameter piston 90. The displacement transmission mechanism 70 partitions the oil tight chamber 71 together with the valve body 40. The oil tight chamber 71 is a flat annular space provided substantially coaxially with the large diameter piston 80 and the small diameter piston 90. The oil-tight chamber 71 is filled with fuel that has entered between the large-diameter piston 80, the small-diameter piston 90, and the valve body 40.

The large-diameter piston 80 is made of a metal material and has a bottomed cylindrical shape. The large-diameter piston 80 is restricted from rotating in the circumferential direction with respect to the valve body 40. The outer diameter of the large-diameter piston 80 is substantially the same as the inner diameter of the cylindrical large-diameter sliding wall portion 46 a that defines the piston housing chamber 42. The large-diameter piston 80 can be displaced in the axial direction along the large-diameter sliding wall portion 46a, and is displaced in a direction in which the fuel in the oil-tight chamber 71 is compressed by the driving force input from the driving unit 30. The large-diameter piston 80 has a bottom wall portion 80a, a peripheral wall portion 80b, and an intermediate member 80c.

The operation of the stroke portion 34a is input to the bottom wall portion 80a through the intermediate member 80c. In addition, the large-diameter piston 80 is pressed against the output piston 34 by the needle spring 63. As described above, the large-diameter piston 80 can be displaced in the axial direction integrally with the stroke portion 34a. A piston communication hole 84 is formed in the bottom wall portion 80a. The piston communication hole 84 is a through hole that penetrates the bottom wall portion 80a in the plate thickness direction. The piston communication hole 84 communicates the inside and outside of the expansion / contraction space 73 in the piston housing chamber 42.

A large-diameter pressure surface 81, a sliding outer peripheral wall portion 82, and a sliding inner peripheral wall portion 83 are formed on the peripheral wall portion 80b. The large diameter pressing surface 81 is formed on the top surface of the peripheral wall portion 80b. The large-diameter pressure surface 81 is a flat surface formed in an annular shape. The large-diameter pressure surface 81 faces the oil-tight chamber 71 and partitions the oil-tight chamber 71. The large-diameter pressurizing surface 81 pressurizes the fuel in the oil-tight chamber 71 by a driving force input from the driving unit 30 to the large-diameter piston 80.

The sliding outer peripheral wall portion 82 is formed on the outer peripheral surface of the peripheral wall portion 80b fitted inside the large diameter sliding wall portion 46a. The sliding outer peripheral wall portion 82 maintains the oil tightness of the oil tight chamber 71 with the large diameter sliding wall portion 46a while allowing the large diameter piston 80 to slide with respect to the large diameter sliding wall portion 46a. . The sliding inner peripheral wall 83 is formed on the inner peripheral surface of the peripheral wall 80b in which the small diameter piston 90 is fitted. The sliding inner peripheral wall 83 enables the small diameter piston 90 to slide with respect to the large diameter piston 80. The sliding inner peripheral wall 83 forms an oil tightness of the oil tight chamber 71 with the small diameter piston 90.

The small diameter piston 90 is formed of a metal material in a two-stage cylindrical shape. The small diameter piston 90 is restricted from rotating in the circumferential direction with respect to the large diameter piston 80 and the valve body 40. The small diameter piston 90 can be displaced relative to the large diameter piston 80 in the axial direction. When the large-diameter piston 80 is displaced in the direction in which the fuel in the oil-tight chamber 71 is compressed by the driving force of the driving unit 30, the small-diameter piston 90 is pushed by the fuel in the oil-tight chamber 71 and is the direction opposite to the large-diameter piston 80. It is displaced to. As described above, the displacement of the large-diameter piston 80, that is, the generated driving force of the driving unit 30 is inverted 180 ° by the fuel in the oil-tight chamber 71 and transmitted to the small-diameter piston 90.

An expansion / contraction space 73 is formed between the small diameter piston 90 and the large diameter piston 80. The expansion / contraction space 73 is a space defined in the piston accommodation chamber 42. The small diameter piston 90 and the large diameter piston 80 are relatively displaced in opposite directions. Therefore, the expansion / contraction space 73 is expanded / contracted with the transmission of the driving force.

A needle insertion hole 98 that penetrates the small diameter piston 90 in the axial direction is formed in the center of the small diameter piston 90 in the radial direction. The nozzle needle 60 is inserted through the needle insertion hole 98. The small diameter piston 90 can be displaced in the axial direction along the sliding inner peripheral wall portion 83. The small diameter piston 90 has an enlarged diameter portion 90a and an internal fitting portion 90b.

The outer diameter of the enlarged diameter portion 90 a is substantially the same as the inner diameter of the sliding inner peripheral wall portion 83. A small-diameter pressure receiving surface 91, a large-diameter inner fitting wall portion 93, and a transmission surface 96 are formed in the enlarged diameter portion 90a. The small diameter pressure receiving surface 91 is formed in a step portion provided between the outer peripheral surface of the enlarged diameter portion 90a and the outer peripheral surface of the inner fitting portion 90b. The small diameter pressure receiving surface 91 is a flat surface formed in an annular shape. The small diameter pressure receiving surface 91 faces the oil-tight chamber 71 and partitions the oil-tight chamber 71. The small-diameter pressure receiving surface 91 receives a force in a direction in which the small-diameter piston 90 is pushed up toward the drive unit from the fuel in the oil tight chamber 71. The area of the small diameter pressure receiving surface 91 is different from the area of the large diameter pressure surface 81. In the first embodiment, the area of the large diameter pressure surface 81 is larger than the area of the small diameter pressure surface 91.

The displacement of the large-diameter piston 80 is expanded by the fuel in the oil-tight chamber 71 and transmitted to the small-diameter piston 90 due to the correlation between the areas of the large-diameter pressure surface 81 and the small-diameter pressure receiving surface 91 described above. On the other hand, due to the expansion of the stroke, the force with which the small diameter piston 90 pushes the nozzle needle 60 becomes weaker than the force with which the stroke portion 34 a pushes the large diameter piston 80.

The large-diameter inner fitting wall portion 93 is formed on the outer peripheral surface of the enlarged-diameter portion 90a fitted into the large-diameter piston 80. The large-diameter inner fitting wall portion 93 allows the sliding inner peripheral wall portion 83 to slide. The large-diameter inner fitting wall portion 93 maintains the oil tightness of the oil tight chamber 71 with the sliding inner peripheral wall portion 83.

The transmission surface 96 is formed on the upper surface of the small diameter piston 90 facing the bottom wall portion 80a. The transmission surface 96 is formed in a flat annular shape substantially orthogonal to the axial direction of the small diameter piston 90. The transmission surface 96 is in contact with the flange 61 urged by the needle spring 63. The transmission surface 96 transmits a driving force in the valve opening direction to the nozzle needle 60. The transmission surface 96 allows positional deviation of the flange 61 in the radial direction and the circumferential direction substantially orthogonal (crossing) to the valve opening direction.

A small diameter inner fitting wall portion 94 and a spring mounting surface 97 are formed in the inner fitting portion 90b. The small-diameter inner fitting wall portion 94 is formed on the outer peripheral surface of the inner fitting portion 90b. The small-diameter inner fitting wall portion 94 is fitted into a cylindrical small-diameter sliding wall portion 46 b that defines the piston housing chamber 42. The small-diameter inner fitting wall portion 94 allows the small-diameter piston 90 to slide relative to the small-diameter sliding wall portion 46b. The small-diameter inner fitting wall portion 94 maintains the oil-tightness of the oil-tight chamber 71 with the small-diameter sliding wall portion 46b.

The spring mounting surface 97 is formed on the top surface of the internal fitting portion 90b. One end of the piston spring 99 in the axial direction is placed on the spring placement surface 97. The piston spring 99 is formed in a coil shape in which a metal wire is wound spirally. The piston spring 99 is disposed in a compressed state between the spring placement surface 97 and a stepped portion 46 c formed on the partition wall of the high-pressure channel 41. The small diameter piston 90 and the nozzle needle 60 can be integrally displaced in the axial direction by the elastic forces of the piston spring 99 and the needle spring 63.

Details of the injection operation of the fuel injection device 100 configured as above will be described in order based on FIGS. 3 and 4.

When application of a drive current in the valve opening direction is started from the engine control device 17 to the drive unit 30, the piezoelectric element laminate 31 expands in the axial direction. As a result, the lower end of the piezoelectric element laminate 31 is displaced in the direction of pushing down the pressure piston 33. The displacement of the lower end of the piezoelectric element laminate 31 is transmitted to the large-diameter piston 80 via the stress relaxation mechanism 32. The large-diameter piston 80 is displaced in the axial direction in synchronization with the movement of the lower end of the piezoelectric element laminate 31.

Due to the displacement of the large-diameter piston 80, the fuel in the oil-tight chamber 71 is compressed by the large-diameter pressure surface 81. Therefore, the small diameter pressure receiving surface 91 of the small diameter piston 90 is pushed by the fuel in the oil tight chamber 71 and lifted. At this time, the volume of the oil-tight chamber 71 that is reduced by the large-diameter pressurizing surface 81 pushing away the fuel and the volume of the oil-tight chamber 71 that is increased by the fuel lifting the small-diameter pressure-receiving surface 91 are substantially the same. As described above, since the area of the large-diameter pressure surface 81 is larger than the area of the small-diameter pressure-receiving surface 91, the displacement amount of the small-diameter piston 90 along the axial direction is larger than the displacement amount of the large-diameter piston 80.

As described above, the displacement transmission mechanism 70 expands the displacement of the large-diameter piston 80 by the fuel in the oil-tight chamber 71 and transmits the displacement to the small-diameter piston 90 in accordance with Pascal's principle. In addition, the displacement of the large-diameter piston 80 is inverted 180 ° by the fuel in the oil-tight chamber 71 and transmitted to the small-diameter piston 90. Thus, the small diameter piston 90 is displaced in the direction opposite to the large diameter piston 80 in synchronization with the movement of the large diameter piston 80. The nozzle needle 60 is lifted in the valve opening direction by the driving force transmitted by the small diameter piston 90. As a result, the main valve portion 50 is opened, and fuel injection from the nozzle hole 44 is started.

The engine control device 17 can control the operating speed and the displacement amount of the piezoelectric element laminate 31 by the drive current applied to the piezoelectric element laminate 31. Therefore, when a drive current is further applied to the piezoelectric element stack 31 during one injection, the lower end of the piezoelectric element stack 31 further pushes down the large-diameter piston 80. As a result, the small-diameter piston 90 and the nozzle needle 60 are further displaced in the valve opening direction, resulting in an increase in the injection rate. As described above, according to the configuration of the fuel injection device 100, the engine control device 17 can arbitrarily change the fuel injection rate.

Then, when a drive current in the valve closing direction is applied from the engine control device 17 to the drive unit 30, the drive force acting on the stress relaxation mechanism 32 from the lower end of the piezoelectric element laminate 31 disappears. Thereby, the lower end of the piezoelectric element laminated body 31, the large-diameter piston 80, and the like are integrally lifted upward by the elastic force of the needle spring 63 and the like. In addition, the small-diameter piston 90 and the nozzle needle 60 are also integrally displaced toward the valve closing direction by the elastic force of the needle spring 63, the fuel pressure, etc., and the main valve portion 50 is closed. Thus, fuel injection from the injection hole 44 is interrupted.

According to the first embodiment described so far, the driving force generated by the driving unit 30 displaces the large-diameter piston 80 in the direction in which the fuel in the oil-tight chamber 71 is compressed. Then, when the small-diameter piston 90 is pushed by the fuel in the oil-tight chamber 71, the generated driving force of the driving unit 30 is transmitted to the nozzle needle 60 after changing the direction in which it acts. As described above, even when the fuel injection device 100 directly displaces the nozzle needle 60 by the driving unit 30 by changing the direction of the driving force by the fuel, the mechanical force resulting from the transmission of the driving force is mechanical. Wear can be reduced.

In addition, in the first embodiment, the displacement generated by the drive unit 30 is expanded by the fuel filling the oil tight chamber 71 and transmitted to the small diameter piston 90 and the nozzle needle 60. With the above configuration, since the displacement amount is increased by the fuel, mechanical wear associated with the displacement amount conversion and transmission can also be reduced.

In the first embodiment, the displacement enlargement ratio of the displacement transmission mechanism 70 is determined by the area ratio of the large-diameter pressure surface 81 and the small-diameter pressure-receiving surface 91 based on the Pascal principle. Therefore, the magnification of displacement in the displacement transmission mechanism 70 can be adjusted by changing the area ratio in the design stage. As described above, the fuel injection device 100 uses the displacement transmission mechanism 70 to change the driving force and the displacement generated by the piezoelectric element stack 31 to a valve opening force and a displacement that are suitable for opening the nozzle needle 60. Can be reliably converted.

Furthermore, in the first embodiment, the displacement transmission mechanism 70 expands the movement of the piezoelectric element laminate 31 by increasing the area of the large-diameter pressure surface 81 to be larger than the area of the small-diameter pressure-receiving surface 91. Communicating. According to the above, even if the piezoelectric element laminate 31 in which it is difficult to secure the displacement amount is used, the fuel injection device 100 directly drives the nozzle needle 60 by the expansion / contraction operation of the piezoelectric element laminate 31 to The part 50 can be opened and closed.

In addition, the transmission surface 96 of the first embodiment allows the positional deviation of the flange portion 61 in the radial direction. Therefore, the inclination of the nozzle needle 60 with respect to the small diameter piston 90 can be absorbed between the transmission surface 96 and the flange 61. With such a configuration, it is possible to prevent the occurrence of stress that causes the small-diameter piston 90 to be inclined and excessively wears the large-diameter inner fitting wall portion 93 and the small-diameter inner fitting wall portion 94.

Further, according to the first embodiment, the direction of displacement of the stroke portion 34 a and the large-diameter piston 80 is reversed by the fuel in the oil-tight chamber 71. Therefore, even if the piezoelectric element laminate 31 generates only a driving force in the direction of pushing down the large-diameter piston 80, the driving force in the direction of pulling up in the valve opening direction is input to the nozzle needle 60.

Further, in the configuration in which the displacement direction is reversed by the fuel in the oil-tight chamber 71 as in the first embodiment, an expansion / contraction space 73 is formed between the large-diameter piston 80 and the small-diameter piston 90 that expands / contracts as the driving force is transmitted. It will be. Therefore, the large-diameter piston 80 is formed with a piston communication hole 84 that communicates the inside and outside of the expansion / contraction space 73. The piston communication hole 84 can suppress the pressure fluctuation of the expansion / contraction space 73 due to the relative displacement of the large-diameter piston 80 and the small-diameter piston 90 by circulating the fuel. According to the above, the situation where the relative displacement of the large diameter piston 80 and the small diameter piston 90 is hindered by the fuel in the expansion / contraction space 73 is avoided.

In addition, the large-diameter piston 80 and the small-diameter piston 90 of the first embodiment form the oil-tightness of the oil-tight chamber 71 by the sliding inner peripheral wall portion 83 and the large-diameter inner fitting wall portion 93 provided respectively. As described above, the size of the displacement transmission mechanism 70 can be kept small as long as no other member is interposed between the pistons 80 and 90. Therefore, it is possible to prevent the fuel injection device 100 from becoming large.

In the first embodiment, the rotation of the large-diameter piston 80 and the small-diameter piston 90 in the circumferential direction is restricted. According to the above configuration, wear caused by rotation of the oil-tight portions of the large-diameter piston 80 and the small-diameter piston 90 is reduced. In addition, according to the rotation restriction of the large-diameter piston 80, the position of the piston communication hole 84 is maintained near the opening of the high-pressure channel 41. Therefore, the high-pressure fuel supplied through the high-pressure channel 41 passes through the piston housing chamber 42 and smoothly flows in the vicinity of the injection hole 44.

In the first embodiment, the high-pressure channel 41 corresponds to the supply channel, the nozzle needle 60 corresponds to the valve member, the large-diameter piston 80 corresponds to the first piston member, and the large-diameter pressure surface 81 is the first. It corresponds to one piston surface. The piston communication hole 84 corresponds to the communication hole, the small diameter piston 90 corresponds to the second piston member, the small diameter pressure receiving surface 91 corresponds to the second piston surface, and the large diameter internal fitting wall portion 93 is the sliding wall portion. The transmission surface 96 corresponds to the transmission unit.

(Second embodiment)
The second embodiment shown in FIGS. 5 to 8 is a modification of the first embodiment. The displacement transmission mechanism 270 of the fuel injection device 200 according to the second embodiment includes a large-diameter piston plate 280, a plurality (four) of small-diameter pistons 290, and a partition plate 275. The displacement transmission mechanism 270 is accommodated in a piston accommodation chamber 242 formed in a columnar shape in the valve body 240 of the second embodiment.

The large diameter piston plate 280 corresponds to the large diameter piston 80 of the first embodiment (see FIG. 2). The large-diameter piston plate 280 can be displaced in the axial direction integrally with the stroke portion 34a. The large-diameter piston plate 280 is displaced in the direction in which the fuel in the oil-tight chamber 271 is compressed by the driving force input from the driving unit 30. The large diameter piston plate 280 includes a plate body 281 and a plurality (four) of large diameter piston rods 285.

The plate body 281 is formed of a metal material into a bottomed cylindrical shape having a bottom wall portion 281a and a peripheral wall portion 281b. The bottom wall portion 281a is formed with a piston communication hole 84 that is substantially the same as in the first embodiment. A piston mounting surface 283 is formed on the peripheral wall portion 281b in addition to the same sliding outer peripheral wall portion 82 as that of the first embodiment.

The piston mounting surface 283 is formed on the top surface of the peripheral wall portion 281b facing the partition plate 275. The piston mounting surface 283 is a flat surface formed in an annular shape. The piston mounting surface 283 is in contact with each end surface of the plurality of large diameter piston rods 285. The piston mounting surface 283 presses each large-diameter piston rod 285 toward the oil-tight chamber 271 by the driving force input from the driving unit 30.

The large-diameter piston rod 285 is formed in a long and narrow cylindrical shape from a metal material. The large-diameter piston rods 285 are arranged at equal intervals along the circumferential direction of the plate body 281 (see FIG. 6). The large diameter piston rod 285 is inserted through a large diameter rod hole 278 provided in the partition plate 275. The large-diameter piston rod 285 is formed with a large-diameter pressure surface 286, a large-diameter pressing surface 287, and a large-diameter rod outer peripheral wall 288.

The large-diameter pressure surface 286 is formed on the first end surface facing the oil-tight chamber 271 among both end surfaces of the large-diameter piston rod 285. The large-diameter pressing surface 286 is a flat surface formed in a perfect circle shape. When the large-diameter piston plate 280 is pushed down by the drive unit 30, the large-diameter pressurizing surface 286 pressurizes the fuel in the oil-tight chamber 271.

The large diameter pressing surface 287 is formed on the second end surface in contact with the piston mounting surface 283 among the both end surfaces of the large diameter piston rod 285. The large-diameter pressure surface 286 is a flat surface formed in a perfect circle shape like the large-diameter pressure surface 286. The large diameter pressing surface 287 is pressed toward the oil-tight chamber 271 by the piston mounting surface 283. The large-diameter pressing surface 287 is allowed to be displaced in the radial direction and the circumferential direction with respect to the piston mounting surface 283.

The large diameter rod outer peripheral wall 288 is formed on the outer peripheral surface of the large diameter piston rod 285. The outer diameter of the large diameter rod outer peripheral wall 288 is approximately the same as the inner diameter of the large diameter rod hole 278. The large-diameter rod outer peripheral wall 288 allows the large-diameter piston rod 285 to slide with respect to the partition plate 275. The large-diameter rod outer peripheral wall 288 maintains the oil-tightness of the oil-tight chamber 271 with the large-diameter rod hole 278.

The small diameter piston 290 corresponds to the small diameter piston 90 (see FIG. 2) of the first embodiment. The small-diameter piston 290 is a member that transmits to the nozzle needle 60 the displacement of the large-diameter piston rod 285 expanded and inverted by 180 ° by the fuel in the oil-tight chamber 271. The small diameter piston 290 is inserted through a small diameter rod hole 279 provided in the partition plate 275. The small diameter pistons 290 are arranged at equal intervals along the circumferential direction of the plate body 281 (see FIG. 6). The small diameter piston 290 and the large diameter piston rod 285 are arranged along the radial direction of the plate body 281.

The small-diameter piston 290 is made of a metal material and has a long and narrow cylindrical shape. The outer diameter of the small diameter piston 290 is smaller than the outer diameter of the large diameter piston rod 285. The axial length of the small diameter piston 290 is substantially the same as the axial length of the large diameter piston rod 285. The small diameter piston 290 is formed with a small diameter pressure receiving surface 291, a small diameter rod outer peripheral wall 293, and a small diameter transmission surface 296.

The small diameter pressure receiving surface 291 is formed on the first end surface facing the oil tight chamber 271 among the both end surfaces of the small diameter piston 290. The small diameter pressure receiving surface 291 is a flat surface formed in a perfect circle. The total area of the small diameter pressure receiving surfaces 291 that is the sum of the areas of the plurality of small diameter pressure receiving surfaces 291 is different from the total area of the large diameter pressing surfaces 286 that is the sum of the areas of the plurality of large diameter pressure receiving surfaces 286. In the second embodiment, the total area of the large-diameter pressure surface 286 is larger than the total area of the small-diameter pressure-receiving surface 291. The small diameter pressure receiving surface 291 receives a force for pushing up the small diameter piston 290 from the fuel in the oil tight chamber 271.

The small diameter rod outer peripheral wall 293 is formed on the outer peripheral surface of the small diameter piston 290. The outer diameter of the small diameter rod outer peripheral wall 293 is approximately the same as the inner diameter of the small diameter rod hole 279. The small diameter rod outer peripheral wall 293 allows the small diameter piston 290 to slide relative to the partition plate 275. The small-diameter rod outer peripheral wall 293 maintains the oil-tightness of the oil-tight chamber 271 with the small-diameter rod hole 279.

The small diameter transmission surface 296 is formed on the second end surface of the small diameter piston 290 that faces the bottom wall portion 281a. The small diameter transmission surface 296 is a perfect circular flat surface that is substantially orthogonal to the axial direction of the small diameter piston 290. On each small diameter transmission surface 296, the flange portion 61 of the nozzle needle 60 is placed. The small diameter transmission surface 296 transmits the driving force in the valve opening direction to the nozzle needle 60 while allowing the displacement of the flange 61 in the radial direction and the circumferential direction substantially orthogonal to the valve opening direction.

The partition plate 275 is formed in a disk shape from a metal material. The partition plate 275 is accommodated in the valve body 240 and is fixed to the valve body 240. In the partition plate 275, a partition wall portion 276, a needle insertion hole 277, a large diameter rod hole 278, and a small diameter rod hole 279 are formed.

The partition wall 276 is an annular recess formed in the lower end surface of the partition plate 275 facing the nozzle hole side. The partition wall 276 partitions a flat annular oil-tight chamber 271 together with the large-diameter pressurizing surface 286, the small-diameter pressure-receiving surface 291 and the bottom wall surface 242a of the piston housing chamber 242. The oil tight chamber 271 is filled with fuel.

The needle insertion hole 277 is a through hole provided in the center of the partition plate 275 in the radial direction. The nozzle needle 60 is inserted through the needle insertion hole 277. The inner diameter of the needle insertion hole 277 is made larger than the outer diameter of the nozzle needle 60. The fuel flows between the needle insertion hole 277 and the nozzle needle 60 and reaches the injection hole 44.

The large diameter rod hole 278 is a through hole penetrating the partition plate 275 in the axial direction. A plurality of large-diameter rod holes 278 are formed at equal intervals along the circumferential direction of the partition plate 275 (see FIG. 7). The large diameter rod hole 278 is fitted on the large diameter piston rod 285. One end of the large-diameter rod hole 278 opens to the ceiling surface of the oil-tight chamber 271. The inner peripheral wall of the large diameter rod hole 278 forms a large diameter outer fitting wall 278a. The large-diameter outer fitting wall 278a forms the oil-tightness of the oil-tight chamber 271 with the large-diameter rod outer peripheral wall 288 while allowing the large-diameter piston rod 285 to slide.

The small diameter rod hole 279 is a through hole penetrating the partition plate 275 in the axial direction. The small diameter rod hole 279 has a smaller diameter than the large diameter rod hole 278. Similar to the large diameter rod hole 278, a plurality of small diameter rod holes 279 are formed at equal intervals along the circumferential direction of the partition plate 275 (see FIG. 7). The small diameter rod hole 279 is located inside the large diameter rod hole 278 in the radial direction. A predetermined interval is provided between the small diameter rod hole 279 and the large diameter rod hole 278 to ensure strength. The small diameter rod hole 279 is fitted on the small diameter piston 290. One end of the small diameter rod hole 279 opens in the ceiling surface of the oil tight chamber 271. The inner peripheral wall of the small diameter rod hole 279 forms a small diameter outer fitting wall 279a. The small-diameter outer fitting wall 279a forms an oil-tight chamber between the small-diameter outer fitting wall 279a and allows the small-diameter piston 290 to slide.

In the fuel injection device 200 having the above configuration, the driving force generated by the expansion of the piezoelectric element laminate 31 is input to the large-diameter piston plate 280 via the stress relaxation mechanism 32, and the oil-tight chamber 271 is Fuel is compressed. As a result, each small-diameter piston 290 pushes up each small-diameter pressure receiving surface 291 by the fuel in the oil-tight chamber 271 and displaces the nozzle needle 60 in the valve opening direction. Thus, fuel injection from the injection hole 44 is started. At this time, since the total area of the large-diameter pressure surface 286 is larger than the total area of the small-diameter pressure-receiving surface 291, the displacement of the large-diameter piston plate 280 is expanded by the fuel in the oil-tight chamber 271. Communicated.

Also, the operation of the piezoelectric element laminate 31 is directly transmitted to the nozzle needle 60 via the displacement transmission mechanism 270. Therefore, the engine control device 17 can change the mode of the injection rate during one injection by controlling the operating speed and the displacement amount of the piezoelectric element laminate 31.

Also in the second embodiment described so far, the direction of the driving force is changed by the fuel in the oil-tight chamber 271. Therefore, the same effects as in the first embodiment can be obtained, and even with the direct-acting fuel injection device 200, mechanical wear associated with transmission of driving force can be reduced.

In addition, in the second embodiment, the sliding portion forming the oil tightness of the oil tight chamber 271 is provided independently on the cylindrical large diameter piston rod 285 and the small diameter piston 290. With such a configuration, the machining of the large-diameter rod outer peripheral wall 288 and the small-diameter rod outer peripheral wall 293 requiring high dimensional accuracy is relatively easy.

In the second embodiment, the large diameter piston plate 280 corresponds to the first piston member, and the large diameter pressurizing surface 286 corresponds to the first piston surface. Further, the small diameter piston 290 corresponds to the second piston member, the small diameter pressure receiving surface 291 corresponds to the second piston surface, and the partition plate 275 corresponds to the partition member. The large-diameter outer fitting wall 278a corresponds to the first sliding wall portion, the small-diameter outer fitting wall 279a corresponds to the second sliding wall portion, and the small-diameter transmission surface 296 corresponds to the transmission portion.

(Other embodiments)
Although a plurality of embodiments have been described above, the present disclosure is not construed as being limited to the above-described embodiments, and can be applied to various embodiments and combinations without departing from the scope of the present disclosure. it can.

In the above embodiment, the sliding inner peripheral wall portion 83 and the large diameter inner fitting wall portion 93, the large diameter rod outer peripheral wall 288 and the large diameter outer fitting wall 278a, and the small diameter rod outer peripheral wall 293 and the small diameter outer fitting wall 279a are between It was formed oil-tight. These oil-tight parts allow for the slow entry of high-pressure fuel from the high-pressure channel into the oil-tight chamber, while substantially preventing leakage from the oil-tight chamber to the high-pressure channel when driving force is transmitted. ing.

In the above embodiment, the driving force generated by the driving unit is inverted 180 ° by the fuel in the oil-tight chamber and transmitted from the large-diameter piston to the small-diameter piston. However, the virtual axis that defines the displacement direction of the large-diameter piston may not be parallel to the virtual axis that defines the displacement direction of the small-diameter piston, and may be defined in a posture inclined with respect to the virtual axis of the small-diameter piston. Good.

In the above embodiment, the area or total area of the large-diameter pressure surface and the area or total area of the small-diameter pressure receiving surface were different from each other. Each area accurately indicates a projected area obtained by projecting the pressure surface and the pressure receiving surface along the displacement axis onto a virtual plane substantially orthogonal to the displacement axis of each piston. If these projected areas are different, the displacement of the large-diameter piston is enlarged or reduced by the fuel and transmitted to the small-diameter piston.

In the above-described embodiment, the displacement transmission mechanism causes the displacement of the driving force to be weakened with the expansion of the stroke by making the area or total area of the large-diameter pressure surface larger than the area or total area of the small-diameter pressure receiving surface. , Was transmitted to the nozzle needle. However, the displacement transmission mechanism transmits the displacement with increased driving force to the nozzle needle as the stroke is reduced by making the pressure area of the large diameter pressure surface smaller than the pressure area of the small diameter pressure surface. It is also possible. Furthermore, the displacement transmission mechanism 70 may be configured to simply change the displacement direction without changing the stroke by equally defining the pressure area of the large diameter pressure surface and the pressure area of the small diameter pressure surface. .

In the above embodiment, the inclination of the nozzle needle is allowed by the configuration in which the small-diameter piston and the nozzle needle are formed of separate members. However, the small diameter piston and the nozzle needle may be integrally formed. An intermediate member for transmitting a driving force may be provided between the small diameter piston and the nozzle needle. Furthermore, the structure corresponding to the first piston member and the second piston member may be one member such as the large diameter piston and the small diameter piston of the first embodiment, or the large diameter piston plate of the second embodiment. And a plurality of members such as small-diameter piston groups.

The displacement transmission mechanism of the above embodiment forms an oil tight chamber in cooperation with the valve body. However, the oil tight chamber may be defined only by the components of the displacement transmission mechanism. Further, the volume and shape of the oil tight chamber may be changed as appropriate.

In the above embodiment, the example in which the characteristic portion of the present disclosure is applied to the fuel injection device that injects light oil as fuel has been described. However, the characteristic portion of the present disclosure injects fuel other than light oil, for example, liquefied gas fuel such as dimethyl ether. It is applicable also to the fuel-injection apparatus which does.

Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

Claims

A fuel injection device for injecting fuel from an injection hole (44),
A valve body (40, 240) in which a supply channel (41) for supplying fuel to the nozzle hole and the nozzle hole is formed;
A valve member (60) for opening and closing the nozzle hole by relative displacement with respect to the valve body;
A drive unit (30) for generating a drive force for displacing the valve member;
A first piston member (80, 280) for partitioning at least a part of the oil-tight chamber (71, 271) filled with fuel and compressing the fuel in the oil-tight chamber by the driving force of the drive unit;
At least a part of the oil tight chamber (71, 271) is partitioned, and when pushed by the fuel in the oil tight chamber, the direction of the driving force input to the fuel in the oil tight chamber is changed and transmitted to the valve member And a second piston member (90, 290).
The fuel injection device according to claim 1, wherein the displacement of the first piston member is substantially inverted by 180 ° by the fuel in the oil-tight chamber and transmitted to the second piston member.
The first piston member has a first piston surface (81,286) facing the oil tight chamber,
3. The fuel injection device according to claim 1, wherein the second piston member has a second piston surface (91, 291) facing the oil-tight chamber and having a different area from the first piston surface.
The fuel injection device according to claim 3, wherein an area of the first piston surface is larger than an area of the second piston surface.
The second piston member is formed with a transmission portion (96, 296) for transmitting a driving force in the valve opening direction to the valve member,
The fuel injection device according to any one of claims 1 to 4, wherein the transmission unit allows a displacement of the valve member in a direction intersecting the valve opening direction.
In the valve body, piston housing chambers (42, 242) for housing the first piston member and the second piston member are formed as a part of the supply flow path,
The first piston member and the second piston member define an expansion / contraction space (73) expanded / contracted by mutual displacement in the piston accommodating chamber,
The fuel injection device according to any one of claims 1 to 5, wherein a communication hole (84) is formed in the first piston member to communicate the inside and outside of the expansion / contraction space in the piston housing chamber. .
The second piston member is formed with a sliding wall portion (93) that allows the first piston member to slide while maintaining oil tightness of the oil tight chamber with the first piston member. The fuel injection device according to any one of claims 1 to 6.
A partition member (275) for partitioning at least a part of the oil tight chamber together with the first piston member and the second piston member;
The partition member includes a first sliding wall portion (278a) that maintains oil tightness of the oil tight chamber with the first piston member while allowing sliding of the first piston member, and the first The second sliding wall portion (279a) for maintaining oil tightness of the oil tight chamber with the second piston member while allowing sliding of the two piston members is formed. The fuel injection device according to any one of claims.
The fuel injection device according to any one of claims 1 to 8, wherein the valve body defines at least a part of the oil tight chamber together with the first piston member and the second piston member.